Some old people with varicose veins must wear support compression stockings to prevent thrombosis and strokes. Let them wear sandals and stockings, it is a matter of health, not your fashion sensibilities.
My 86 year old aunt wears support stockings under leggings, at times reversed, with sandals. Her leggings are bright, multi colored designs, from the abstract to florals, and in general I've never seen another woman wear as many colors at one time. Her dresses, blouses, skirts, slacks, vests, are brilliant, loud, and accompanied by a ton of multi colored costume jewelry flashing her presence. She always wears sandals, and living in southern Florida, the weather accommodates her.
She is a fashion abomination, yet she's having fun, pulls it off, and stays alive and well.
As her 14 year old great, great granddaughter says, "She is living art."
Worse, my uncle, 89, her husband wears multi colored printed Guayabera shirts, bermuda shorts even louder, support hose, and sandals, with straw fedoras and sunglasses that are way too big. Better than his smelly gnarly feet. An assault on the eyes, but at his age, he also pulls it off with aplomb.